Question

A concave mirror of focal length $F$ produces a real image $n$ times the size of the object. The distance of the object from the mirror will be $\frac{n+1}{n}F$

• A. True
• B. False

Answer 1

The correct option is A True

From the mirror equation we have,

$\frac{1}{v}+\frac{1}{u}=\frac{1}{f}=\frac{1}{-F}$(Following sign convention)

Also magnification $=\frac{-v}{-u}=n$ (Since image is real and inverted)

$⟹v=nu$

Using this in mirror equation gives,

$u=-\frac{(n+1)F}{n}$

According to sign convention, this is the negative of the distance between object and mirror.

Thus distance between object and mirror $=\frac{(n+1)}{n}F$